The Correlation Between Microbleeds And Cnm-positive Streptococcus Mutans: A Pilot Survey Study Based On Magnetic Resonance Imaging

INTRODUCTION: Oral bacteria variants have been reported to promote hemorrhagic strokes in the animal model (Nakano et al. Nat Commun. 2011). The Collagen-binding protein, Cnm, is secreted by special Streptococcus mutans bacteria and binds to intracranial tissue to cause the promotion of bleeding. On the other hand, presence of microbleeds is reported to be significantly associated with cognitive dysfunction in patients with vascular dementia (Won Seo et al. Stroke. 2007). The purpose of this study is to clarify whether infection with S. mutans that carry the cnmgene is associated with human MRI findings that indicate white matter lesions and microbleeds.

METHODS: The subjects included 145 participants (89 men, 56 women) who had voluntarily undergone a health examination and brain MRI in 2003, 2008 ,2013 and completed 10 years of follow-up. We obtained information on the deep white matter lesion (DWL), which were graded semi-quantitatively according to the Fazekas classification. Based on the SWI finings, subjects were divided into two groups, a microbleeds-positive and negative group. We evaluated cognitive functions using the Mini-Mental State Examination (MMSE),letter and word fluency tasks. To determine which of the main parameters have a significant effect on micobleeds or DWL, clinical vascular risk factors were examined.The subjects included 145 participants (89 men, 56 women) who had voluntarily undergone a health examination and brain MRI in 2003, 2008, 2013 and completed 10 years of follow-up. We obtained information on the deep white matter lesion (DWL), which were graded as semi-quantitatively according to the Fazekas classification. Based on the SWI finings, subjects were divided into two groups, a microbleeds-positive and negative group. We evaluated cognitive functions using the Mini-Mental State Examination (MMSE), letter and word fluency tasks. To determine which of the main parameters have a significant effect on micobleeds or DWL, clinical vascular risk factors were also examined.
RESULTS: 70.6% of the subjects with microbleeds were cnm-positive, whereas only 7.9% of subjects with microbleeds were cnm-negative. When we focus on microbleeds and the numbers of microbleed spots, there appears to be a significant correlation with the exposure of the cnm gene (p<0.01). Letter-fluency test results had a tendency to decrease with the cnm gene positive groups. The odds ratio for microbleeds was 40.6 in cnm-positive subjects compared with cnm-negative subjects without microbleeds (p<0.01). The ratio was even higher after adjusting for age, sex, hypertension and the use of antiplatelet drugs.When we compared the DWL categories, no significant difference was found.
CONCLUSIONS:  Oral Health and intracranila lesions were correlated with each other from our epidemiological survey. There was a strong independent correlation between the frequency of cnm gene-positive S. mutans and the frequency of microbleeds. Thus, this finding suggests that having S. mutans with cnm gene is an independent risk factor for microbleeds. This means that having cnm expression directly leads to an increase in microbleeds, which may be a promoter of concomitant cognitive decline in the field of the elderly population.